1) Field of the Invention
This invention relates generally to a method for forming an inductor for a semiconductor device and more specifically to a method for plating a gold layer using an electroless process.
2) Description of the Prior Art
The communications field requires high frequency products for portable applications in the RF and microwave frequency ranges. The integrated circuits that help meet tasks need generally require passive components such as capacitors and inductors for tuning, LC tanks, AC coupling, impedance matching and filtering requirements. However, with regard to inductors, integrating inductors on the same substrate with active and/or passive components has been problematic. Moreover, the inductor resistance must be reduced to improve device performance.
Gold is an attractive material from which to fabricate inductor elements. However, conventional methods of forming gold inductors, such as electrolytic plating and sputtering, have not been successful. The processes are costly and often involve harmful/detrimental etch steps. There is a need for improved methods to form inductors that have lower resistance, lower costs, and less process etch steps.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering U.S. Pat. No. 5,266,519(Iwanoto) which shows a method of forming a metal conductor using a selective deposition of Gold. U.S. Pat. No. 5,308,796(Feldman) shows a method of selectively depositing Cu over a metal silicide. U.S. Pat. No. 3,993,808(Inaba et al.) shows a method of electroless plating Gold on Tungsten. U.S. Pat. No. 5,242,861(Inaba) show a method of forming a multi-layered structure having a gold under layer. U.S. Pat. No. 5,272,111(Kosaki) shows a method of forming a contact having a Au deposited on a Ni--P layer. U.S. Pat. No. 5,478,773(Dow) shows a Copper inductor. Burghartz et al., "High -Q inductors in Standard Silicon Interconnect Technology and its Application to an Integrated RF Power Amplifier", IEDM 95, pp. 1015 to 1017, discussed inductors. Yamaguchi et al., "Characteristics And Analysis Of A Thin Film Inductor With Closed Magnetic Circuit Structure", IEEE transaction on Magnetic, Vol. 82, No. 5, September 1992, pp. 3015 to 3017 discusses RF sputtering Ni--FE--MO--Cu permalloy films.
However, an improved method is needed to form an inductor for a semiconductor device that uses an electroless process.